Lockdown behaviour?!

[Winginitt]

Anyone else noticing a huge change in their child's behaviour since lockdown started?! My DD is 4, turning 5 in a couple of months and I'm at my wits end with her behaviour. First it started with bedtime, we have always had a really good routine, bath, biscuit, story, bed by 7.30pm, she will usually play a little then is asleep before 8 and has never been disruptive. Since the first week of lockdown we've kept to the same routine but she will be up till 11pm, constantly in and out of her bedroom. Last night was the last straw when she came downstairs at 10pm and point black told me and her dad that she wasn't going back to bed, when told this wasn't good behaviour she simply said 'I don't care'. I don't think we've had an easy bedtime since the start of this. So that's issue number 1. She has become extremely cheeky and dismissive which is so draining, no matter what I ask her to do it's no, she is nearly 5 now and is constantly trashing the house, toys being brought down from her bedroom, she will play with them then when asked to put them back after finishing she refuses, (this is every single day) I've taken some away after getting tired of asking and she has said again 'I don't care'. If she doesn't get her own way with something she starts a really huge tantrum, I'm quite strong willed and will totally ignore it until she's calmed down but then within minutes of us talking about how that wasn't good behaviour she's back to it again. She cannot take no for an answer. Home schooling has become a chore for both of us, she does roughly an hour a week of just phonics and maths and the rest of the time we spend that exploring, painting, crafts etc. If we did any more we'd both lose the plot. I have behaviour charts, I ignore bad behaviour as best as I can, I praise when she is good (becoming a rarity), I limit tablet/tv time, any spare time I have I give to her but nothing seems to be working.
I just feel so drained, she has gone from the loveliest little girl, always kind to someone I'm frightened to discipline because I know the uproar it will cause. I understand how lockdown must be for the little ones, I've struggled myself, we have done so many zoom calls with her friends, and recently a social distanced walk which she handled really well. I never have an issue taking her out she is as good as gold, she's also never had a problem at school, she's really well behaved there. Just at home she is so challenging. The backchatting and down right cheek is really getting to me.
Any advice??

[NuffSaidSam]

The sleeping is a problem lots and lots of people are having and I think it's just due to not being tired. They're not getting the physical, mental or social stimulation that they were pre-lockdown. It's almost impossible to give them that at home, but I would work on increasing that as much as possible.

Try and get out for a few hours each day, lots of fresh air and exercise. Just being somewhere different will be more tiring than being at home. You could also do some YouTube workouts, there are loads and loads (HIIT for kids, ballet, dance, yoga etc.).

Try and stretch her mentally as well, it doesn't have to be home schooling, but if you can think of anything new to do with her/anything that will challenge her mentally that would help I think.

And do as much social stuff as you can.

If you get the sleep sorted, behaviour should improve as well.

It's incredibly difficult though and I don't think it will be fully resolved until we get back to 'normal'.